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Use of Nanostructures in Fabrication of Large Scale Electrochemical Film
Available online at www.sciencedirect.com
Physics Procedia 25 (2012) 44 – 49
2012 International Conference on Solid State Devices and Materials Science
Use of Nanostructures in Fabrication of Large Scale Electrochemical Film Chien Chon Chena*, Shih Hsun Chena, Sheang Wen Shyub, Sheng Jen Hsiehc a Department of Energy Engineering, National United University, 2, Lienda, Miaoli 36003 Taiwan Department of Mechanical Engineering, National United University, 2, Lienda, Miaoli 36003 Taiwan c Department of Engineering Technology and Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3367 b
Abstract Control of electrochemical parameters when preparing small-scale samples for academic research is not difficult. In mass production environments, however, maintenance of constant current density and temperature become a critical issue. This article describes the design of several molds for large work pieces. These molds were designed to maintain constant current density and to facilitate the occurrence of electrochemical reactions in designated areas. Large-area thin films with fine nanostructure were successfully prepared using the designed electrochemical molds and containers. In addition, current density and temperature could be controlled well. This electrochemical system has been verified in many experimental operations, including etching of Al surfaces; electro-polishing of Al, Ti and stainless steel; and fabrication of anodic alumina oxide (AAO), Ti-TiO2 interference membrane, TiO2 nanotubes, AAO-TiO2 nanotubes, Ni nanowires and porous tungsten
© 2012 2011 Published Published by by Elsevier Elsevier B.V. Ltd. Selection organizer] © Selection and/or and/or peer-review peer-review under under responsibility responsibility of of [name Garry Lee Keywords: electrochemical molds, electro-polishing, anodic alumina oxide.
1. Introduction Surface treatment has been used in 3C industries (Computer, Communication, and Consumption electronics production) for decades [1-3]. Consumers are always attracted to 3C products with high surface quality. Because electrochemicals can accurately control current density in a small range (nAˊcm-2), high quality, low cost surface treatments can be achieved using electrochemical processes. Schematic diagrams of basic electrochemical reactions typically include a working electrode, counter electrode, and electrolyte. The restricted reaction area on the working electrode is usually protected using acid/base-resistive adhesive tape. Small samples generated for use in laboratory experiments are easily
1875-3892 © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of Garry Lee doi:10.1016/j.phpro.2012.03.047
Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
controlled because the heat effect is small enough to be ignored in the reaction. However, when producing samples of larger size and quantities, the exothermic and endothermic reactions can affect the bath temperature. This study describes the design of a system for an electrochemical process that includes a mold, bath, and heat change pipe. This system improved a large size product’s electrochemical treatment quantity. 2. Electrochemical mold structure Figure 1 shows a rotating electrochemical mold. Figure 1(a) shows the mold structure, which includes a conducting rod, sample base, and top cover with a designated reaction area. The mold has a large active area that can be exposed to the electrolyte. The top cover of the mold and the bottom substrate are made of insulating materials. A sample of metal foil is sandwiched in the mold and a silicone gel sheet is used to prevent electrolytic leaking into the mold. Working electrodes with copper rods are inside the plastic tube and contact the metal sample. Pressure is applied to the silicone gel sheet to keep the top cover and bottom substrate in close. The advantages of this mold include convenient loading and unloading of the sample, easy-to-control sample reaction area, uniform current density on the sample surface, and prevention of electrolyte leaking. Figure 1(b) shows an exploded view of the mold including rotating cover, O-ring, metal plate, sample base. Figure 1(c) shows a schematic diagram of the mold inside the electrolytic bath. Figure 1(d) shows a schematic diagram of the mold inside the electrochemical system. Figure 2 shows images of anodic aluminium oxide made using the rotating electrochemical mold. Figure 2(a) shows a four-inch diameter sample of transparent AAO film made after removal of the Al substrate of anodic aluminium. Figure 2(b) shows transparent AAO film on a six-inch silicon wafer when the evaporation Al film was anodized. Figure 2(c) shows transparent AAO film on four-inch diameter glass. Figure 3 shows a flat electrochemical mold. Figure 3(a) shows the counter electrode net fixed between two insulated boards with openings in the middle. Figure 3(b) shows a working electrode fixed between silicone gel sheets and electrolytic bath fixed above the working electrode. Figure 4(c) shows the fully assembled mold with the counter electrode fixed on top of the working electrode structure. The flat mold has some advantages over the rotating mold. For example, (1) the gas generated by the electrochemical reaction does not stay on the counter electrode net. (2) Because the design does not include a metal plate, conducting rod, and metal base, the materials cost is reduced and the likelihood of electrolyte leaking was decreased. (3) Because the counter electrode sits directly over the working electrode, the mold integration is achieved. (4) The active open area on the top board can have various shapes. (5) the available sample area is increased because of the use of a square board design. 3. Electrolytic bath structure Figure 4(a) shows an electrochemical system that includes chemical reaction bath, cooling bath, heat change bath, heat change tube, air compressor, and glandless pump. In order to obtain a constant temperature in the chemical reaction bath during electrochemical reactions, the chemical reaction bath, cooling bath, and heat change bath are connected. The heat change tube is set inside the heat change bath and a glandless pump is used for electrolyte flow between the heat change bath and the chemical reaction bath. The water pump circulates ethylene glycol antifreeze between the cooling bath and the heat change bath. Figure 4(b) shows the heat change tube structure, which consists of pipes, elbows, and connecting tubes made of silicone gel. This flexible structure can be extended to form various shapes to fit the heat change bath. Figure 4(c) shows the chemical reaction bath, which consists of electrolyte input and output ports, air input port, and pumping vacuum ports. The electrolyte input is diverted to four inlets. This
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allows the chemical reaction bath to maintain a more constant temperature and electrolyte agitation than a design that has only one electrolyte inlet.
4. Electrolytic bath and mold-assisted surface treatment of materials To evaluate the performance of the designed electrochemical molds and bath, we performed several tests, including chemical etching, electro-polishing, electro-plating, and sol-gel experimental test. In these tests, various chemical solutions were placed in the electrolytic bath, and gas input, agitation, and constant temperature were controlled by air compressor, glandless pump, water bath, ethylene glycol, and the heat change tube assembly. Figure 5 shows images of the surfaces of several types of materials after using the electrochemical bath and mold-assisted surface treatment. Figure 5(a) shows aluminium surface wet etching, in which the operation method consisted of loading aluminium (Al) foil in the mold and immersing the mold in a chemical solution (60 vol.% H2SO4+30 vol.% H3PO4+10 vol.% HNO3) at 100oC for 2~5 minutes. Figure 5(b) shows a 4-inch electro-polished aluminium surface, in which the operation method consisted of loading aluminium (Al) foil in the mold and immersing the mold in electrolyte (15 vol.% HClO4 + 15 vol.% CH3(CH2)3OCH2CH2OH + 15 vol.% C2H6O) at 100oC, at 42 volts (V) for 10 minutes. Figure 5(c) is an optical micro-image showing a clean and scratch-free electro-polished Al surface. Figure 5(d) is an SEM image of anodic aluminium oxide template, for which the fabrication process [4-7] included the following steps: (1) Polish the aluminum (Al) substrate (99.7%), then anneal in an air furnace at 550ºC; (2) Electro-polish the Al substrate in a electrolytic bath, (3) First anodization – Polish the Al substrate with 200V DC in 1 vol.% H3PO4 solution for 30 minutes; (4) Remove the first anodization film by soaking in a solution of 1.8 wt.% CrO3 + 6 vol.% H3PO4 for 40 minutes; (5) Second anodization – Repeat anodization using the solution from the first anodization, but for a longer time (several hours) to form AAO films of varying thickness; (6) Remove the Al substrate by soaking in a solution of 20 wt.%CuCl2 + 8 wt.% HCl for 30 minutes; and (7) Widen the pore diameter of the AAO template by soaking in a 5 vol.% H3PO4 solution for 20 minutes. Figure 5(e) is an optical micro-image showing a clean and scratch-free electropolished Ti surface, for which the operation method included loading titanium (Ti) foil in a mold and immersing the mold in electrolyte (5 vol.% HClO4 + 53 vol.% CH3(CH2)3OCH2CH2OH + 42 vol.% CH3OH) at 15oC, 52V for 15 minutes. Figure 5(f) is an optical microstructure image of Ti-TiO2 interference membrane, for which the operation method included loading electro-polished Ti foil in a mold and immersing the mold in electrolyte (10 vol.% H2SO4 + 53 vol.% CH3(CH2)3OCH2CH2OH + 42 vol.% CH3OH) at 25oC, 10V for 10 seconds. Figure 5(g) shows anodic film on 6-inch diameter titanium foil, for which the operation method included loading the Ti foil in a mold and immersing the mold in electrolyte (0.25 wt.% NH4F + 2vol.% H2O+C2H4(OH)2) at 25oC, 60V for a film forming rate of 12ȝm/hr [8-10]. Figure 5(h) is an SEM image showing TiO2 nanotubes with 120 pore size, 20 nm pore wall thickness, 8×109 tubeˊcm-2 pore density, 78.62% porosity structure. Figure 5(i) is an optical microimage showing a clean scratch-free electro-polished surface of 304 stainless steel (S.S.), for which the operation method included loading S.S. plate in a mold and immersing the mold in electrolyte (25 vol.% H2SO4 + 47 vol. H3PO4+28 vol.% C2H4O3) at 80oC, 0.1 Aˊcm-2 for 3 minutes. Figure 5(j) is an SEM image of nickel (Ni) nano-wires in AAO template, for which the operation method included loading AAO template in a mold and immersing the mold in electrolyte (33wt.% NiSO4•6H2O+4.5wt.% NiCl•6H2O+ 3.7wt.% H3BO3+0.05 vol.% H2O2ˈpH=3.5) at 60oC, 0.8 Aˊcm-2 for 5 minutes. Figure 5(j) is an SEM image showing porous WO3 film, for which the operation method included loading tungsten foil in a mold and immersing the mold in electrolyte (0.1 wt.% KF solution, pH above than 3.5) at 25oC, 30V for 30 minutes. Figure 5(k) is an SEM image of AAO-TiO2 nanotube composite, for which the operation
Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
method included loading AAO template in a mold and immersing the mold in electrolyte (0.2M TiCl4 solution, pH value between 1.0 and 1.3 for 20 min), then adjusting the pH value to 3.0 at 25oC, for 100 minutes immersion.
5. Conclusion This study describes the design and fabrication of a rotating electrochemical mold and a flat electrochemical mold. Electrochemical experimental testing of these molds have demonstrated advantages such as convenient loading and unloading of samples, easy-to-control reaction area of sample, and resistance to electrolyte leaking. Because these molds was made of inexpensive and environment friendly materials such as glass, ceramic, plastic, and acrylic, they can be produced on a large scale for industry. We also designed and fabricated an electrochemical bath that addresses endothermic and exothermic issues and keeps temperature constant during electrochemical reactions in large size samples. The electrochemical bath consists of an electrolytic bath, air compressor, glandless pump, water bath, and assembly heat change tubes. The electrochemical experiment tests included aluminium surface wet etching, electro-polishing on a 4-inch aluminium surface, electro-polishing on a 4 inch titanium surface, fabrication of 4-inch AAO template, fabrication of Ti-TiO2 interference membrane microstructure, fabrication of 6-inch TiO2 nanotube film, and electro-polishing of stainless steel. Acknowledgements This study was partially supported by a grant from the National Science Council, Taiwan (100-2918-I239-001-). References [1] J. Borowski, K. Bartkowiak, Physics Procedia 2010;5A: 449. [2] M. Chemingui, M. khitouni, G. Mesmacque, A.W. Kolsi, Physics Procedia 2009;2:1167. [3] A.J. Eifert, J.P. Thomas and R.G. Rateick, Scripta Materialia (1999);40:929. [4] G. E. Thompson and G. C. Wood: Trans. Inst. Metal Finishing (1980);58: 21. [5] H. Masuda and H. Yamada: Appl. Phys. Lett. 71 (1997) 2770. [6] K. T. Sunil and C. C.Hsueh: Chaos 12 (2002), 240. [7] H. Masuda and F. Hasegwa: J. Electrochem. Soc. (1997);144:127. [8] M. Paulose, H.E. Prakasam, O.K. Varghese, L. Peng, K.C. Popat, G.K. Mor, T.A. Desai, C.A. Grimes, J. Phys. Chem. C (2007);111:14992. [9] C.C. Chen, S. J, Hsieh, Journal of The Electrochemical Society, (2010);156:K125. [10] C.C. Chen, W .D. Jehng , L.L. Li, W.G. Diau, Journal of The Electrochemical Society, (2009);156:C304.
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(a)
(c)
(b)
(d)
tophead O-ring plat e bas
Figure 1. Structure of rotating electrochemical mold: (a) the mold includes conducting rod, sample base, and reaction area; (b) exploded view of the mold showing rotating cover, O-ring, metal plate, and sample base; (c) schematic diagram of mold inside electrolytic bath, (d) schematic diagram of mold inside electrochemical system.
Figure 2 Thin films with nanostructure fabricated using the electrochemical mold and electrolytic bath: (a) four-inch diameter transparent AAO film; (b) transparent AAO film on a six-inch silicon wafer, (c) transparent AAO film on four-inch diameter glass.
(a) dead plate counter
dead plate
(b)
(c)
electrolyte silicone film working silicone film dead plate
Figure 3. Structure of flat electrochemical mold: (a) the counter electrode is fixed between two insulated boards with opening in middle; (b) the working electrode is fixed between silicone gel sheets and electrolytic bath is fixed on top of the working electrode; (c) the mold with counter electrode fixed on the working electrode structure.
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Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
(a) heat change air Heat change tube
electrolyt
pump cooling
(b)
air input
(c
electrolyte input 1 2 4 3 electrolyte output
Figure 4. Electrochemical system including: (a) chemical reaction bath, cooling bath, heat change bath; (b) heat change tube consisting of pipes, elbows, and silicone gel tube connectors; (c) chemical reaction bath consisting of electrolyte input/output ports, air input port, and vacuum ports.
Figure 5. Electrolytic bath and mold-assisted surface treatments: (a) aluminium surface wet etching; (b) electro-polished 4inch aluminium surface; (c) microstructure of electro-polished aluminium; (d) microstructure of AAO template; (e) microstructure of electro-polished titanium; (f) Ti-TiO2 interference membrane microstructure; (g) anodic film on 6-inch titanium foil; (h) TiO2 nanotube microstructure; (i) electro-polished stainless steel microstructure, (j) nano-nickel wires microstructure; (k) porous WO3 microstructure; (l) AAO-TiO2 nanotube composite microstructure.
Physics Procedia 25 (2012) 44 – 49
2012 International Conference on Solid State Devices and Materials Science
Use of Nanostructures in Fabrication of Large Scale Electrochemical Film Chien Chon Chena*, Shih Hsun Chena, Sheang Wen Shyub, Sheng Jen Hsiehc a Department of Energy Engineering, National United University, 2, Lienda, Miaoli 36003 Taiwan Department of Mechanical Engineering, National United University, 2, Lienda, Miaoli 36003 Taiwan c Department of Engineering Technology and Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3367 b
Abstract Control of electrochemical parameters when preparing small-scale samples for academic research is not difficult. In mass production environments, however, maintenance of constant current density and temperature become a critical issue. This article describes the design of several molds for large work pieces. These molds were designed to maintain constant current density and to facilitate the occurrence of electrochemical reactions in designated areas. Large-area thin films with fine nanostructure were successfully prepared using the designed electrochemical molds and containers. In addition, current density and temperature could be controlled well. This electrochemical system has been verified in many experimental operations, including etching of Al surfaces; electro-polishing of Al, Ti and stainless steel; and fabrication of anodic alumina oxide (AAO), Ti-TiO2 interference membrane, TiO2 nanotubes, AAO-TiO2 nanotubes, Ni nanowires and porous tungsten
© 2012 2011 Published Published by by Elsevier Elsevier B.V. Ltd. Selection organizer] © Selection and/or and/or peer-review peer-review under under responsibility responsibility of of [name Garry Lee Keywords: electrochemical molds, electro-polishing, anodic alumina oxide.
1. Introduction Surface treatment has been used in 3C industries (Computer, Communication, and Consumption electronics production) for decades [1-3]. Consumers are always attracted to 3C products with high surface quality. Because electrochemicals can accurately control current density in a small range (nAˊcm-2), high quality, low cost surface treatments can be achieved using electrochemical processes. Schematic diagrams of basic electrochemical reactions typically include a working electrode, counter electrode, and electrolyte. The restricted reaction area on the working electrode is usually protected using acid/base-resistive adhesive tape. Small samples generated for use in laboratory experiments are easily
1875-3892 © 2012 Published by Elsevier B.V. Selection and/or peer-review under responsibility of Garry Lee doi:10.1016/j.phpro.2012.03.047
Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
controlled because the heat effect is small enough to be ignored in the reaction. However, when producing samples of larger size and quantities, the exothermic and endothermic reactions can affect the bath temperature. This study describes the design of a system for an electrochemical process that includes a mold, bath, and heat change pipe. This system improved a large size product’s electrochemical treatment quantity. 2. Electrochemical mold structure Figure 1 shows a rotating electrochemical mold. Figure 1(a) shows the mold structure, which includes a conducting rod, sample base, and top cover with a designated reaction area. The mold has a large active area that can be exposed to the electrolyte. The top cover of the mold and the bottom substrate are made of insulating materials. A sample of metal foil is sandwiched in the mold and a silicone gel sheet is used to prevent electrolytic leaking into the mold. Working electrodes with copper rods are inside the plastic tube and contact the metal sample. Pressure is applied to the silicone gel sheet to keep the top cover and bottom substrate in close. The advantages of this mold include convenient loading and unloading of the sample, easy-to-control sample reaction area, uniform current density on the sample surface, and prevention of electrolyte leaking. Figure 1(b) shows an exploded view of the mold including rotating cover, O-ring, metal plate, sample base. Figure 1(c) shows a schematic diagram of the mold inside the electrolytic bath. Figure 1(d) shows a schematic diagram of the mold inside the electrochemical system. Figure 2 shows images of anodic aluminium oxide made using the rotating electrochemical mold. Figure 2(a) shows a four-inch diameter sample of transparent AAO film made after removal of the Al substrate of anodic aluminium. Figure 2(b) shows transparent AAO film on a six-inch silicon wafer when the evaporation Al film was anodized. Figure 2(c) shows transparent AAO film on four-inch diameter glass. Figure 3 shows a flat electrochemical mold. Figure 3(a) shows the counter electrode net fixed between two insulated boards with openings in the middle. Figure 3(b) shows a working electrode fixed between silicone gel sheets and electrolytic bath fixed above the working electrode. Figure 4(c) shows the fully assembled mold with the counter electrode fixed on top of the working electrode structure. The flat mold has some advantages over the rotating mold. For example, (1) the gas generated by the electrochemical reaction does not stay on the counter electrode net. (2) Because the design does not include a metal plate, conducting rod, and metal base, the materials cost is reduced and the likelihood of electrolyte leaking was decreased. (3) Because the counter electrode sits directly over the working electrode, the mold integration is achieved. (4) The active open area on the top board can have various shapes. (5) the available sample area is increased because of the use of a square board design. 3. Electrolytic bath structure Figure 4(a) shows an electrochemical system that includes chemical reaction bath, cooling bath, heat change bath, heat change tube, air compressor, and glandless pump. In order to obtain a constant temperature in the chemical reaction bath during electrochemical reactions, the chemical reaction bath, cooling bath, and heat change bath are connected. The heat change tube is set inside the heat change bath and a glandless pump is used for electrolyte flow between the heat change bath and the chemical reaction bath. The water pump circulates ethylene glycol antifreeze between the cooling bath and the heat change bath. Figure 4(b) shows the heat change tube structure, which consists of pipes, elbows, and connecting tubes made of silicone gel. This flexible structure can be extended to form various shapes to fit the heat change bath. Figure 4(c) shows the chemical reaction bath, which consists of electrolyte input and output ports, air input port, and pumping vacuum ports. The electrolyte input is diverted to four inlets. This
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Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
allows the chemical reaction bath to maintain a more constant temperature and electrolyte agitation than a design that has only one electrolyte inlet.
4. Electrolytic bath and mold-assisted surface treatment of materials To evaluate the performance of the designed electrochemical molds and bath, we performed several tests, including chemical etching, electro-polishing, electro-plating, and sol-gel experimental test. In these tests, various chemical solutions were placed in the electrolytic bath, and gas input, agitation, and constant temperature were controlled by air compressor, glandless pump, water bath, ethylene glycol, and the heat change tube assembly. Figure 5 shows images of the surfaces of several types of materials after using the electrochemical bath and mold-assisted surface treatment. Figure 5(a) shows aluminium surface wet etching, in which the operation method consisted of loading aluminium (Al) foil in the mold and immersing the mold in a chemical solution (60 vol.% H2SO4+30 vol.% H3PO4+10 vol.% HNO3) at 100oC for 2~5 minutes. Figure 5(b) shows a 4-inch electro-polished aluminium surface, in which the operation method consisted of loading aluminium (Al) foil in the mold and immersing the mold in electrolyte (15 vol.% HClO4 + 15 vol.% CH3(CH2)3OCH2CH2OH + 15 vol.% C2H6O) at 100oC, at 42 volts (V) for 10 minutes. Figure 5(c) is an optical micro-image showing a clean and scratch-free electro-polished Al surface. Figure 5(d) is an SEM image of anodic aluminium oxide template, for which the fabrication process [4-7] included the following steps: (1) Polish the aluminum (Al) substrate (99.7%), then anneal in an air furnace at 550ºC; (2) Electro-polish the Al substrate in a electrolytic bath, (3) First anodization – Polish the Al substrate with 200V DC in 1 vol.% H3PO4 solution for 30 minutes; (4) Remove the first anodization film by soaking in a solution of 1.8 wt.% CrO3 + 6 vol.% H3PO4 for 40 minutes; (5) Second anodization – Repeat anodization using the solution from the first anodization, but for a longer time (several hours) to form AAO films of varying thickness; (6) Remove the Al substrate by soaking in a solution of 20 wt.%CuCl2 + 8 wt.% HCl for 30 minutes; and (7) Widen the pore diameter of the AAO template by soaking in a 5 vol.% H3PO4 solution for 20 minutes. Figure 5(e) is an optical micro-image showing a clean and scratch-free electropolished Ti surface, for which the operation method included loading titanium (Ti) foil in a mold and immersing the mold in electrolyte (5 vol.% HClO4 + 53 vol.% CH3(CH2)3OCH2CH2OH + 42 vol.% CH3OH) at 15oC, 52V for 15 minutes. Figure 5(f) is an optical microstructure image of Ti-TiO2 interference membrane, for which the operation method included loading electro-polished Ti foil in a mold and immersing the mold in electrolyte (10 vol.% H2SO4 + 53 vol.% CH3(CH2)3OCH2CH2OH + 42 vol.% CH3OH) at 25oC, 10V for 10 seconds. Figure 5(g) shows anodic film on 6-inch diameter titanium foil, for which the operation method included loading the Ti foil in a mold and immersing the mold in electrolyte (0.25 wt.% NH4F + 2vol.% H2O+C2H4(OH)2) at 25oC, 60V for a film forming rate of 12ȝm/hr [8-10]. Figure 5(h) is an SEM image showing TiO2 nanotubes with 120 pore size, 20 nm pore wall thickness, 8×109 tubeˊcm-2 pore density, 78.62% porosity structure. Figure 5(i) is an optical microimage showing a clean scratch-free electro-polished surface of 304 stainless steel (S.S.), for which the operation method included loading S.S. plate in a mold and immersing the mold in electrolyte (25 vol.% H2SO4 + 47 vol. H3PO4+28 vol.% C2H4O3) at 80oC, 0.1 Aˊcm-2 for 3 minutes. Figure 5(j) is an SEM image of nickel (Ni) nano-wires in AAO template, for which the operation method included loading AAO template in a mold and immersing the mold in electrolyte (33wt.% NiSO4•6H2O+4.5wt.% NiCl•6H2O+ 3.7wt.% H3BO3+0.05 vol.% H2O2ˈpH=3.5) at 60oC, 0.8 Aˊcm-2 for 5 minutes. Figure 5(j) is an SEM image showing porous WO3 film, for which the operation method included loading tungsten foil in a mold and immersing the mold in electrolyte (0.1 wt.% KF solution, pH above than 3.5) at 25oC, 30V for 30 minutes. Figure 5(k) is an SEM image of AAO-TiO2 nanotube composite, for which the operation
Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
method included loading AAO template in a mold and immersing the mold in electrolyte (0.2M TiCl4 solution, pH value between 1.0 and 1.3 for 20 min), then adjusting the pH value to 3.0 at 25oC, for 100 minutes immersion.
5. Conclusion This study describes the design and fabrication of a rotating electrochemical mold and a flat electrochemical mold. Electrochemical experimental testing of these molds have demonstrated advantages such as convenient loading and unloading of samples, easy-to-control reaction area of sample, and resistance to electrolyte leaking. Because these molds was made of inexpensive and environment friendly materials such as glass, ceramic, plastic, and acrylic, they can be produced on a large scale for industry. We also designed and fabricated an electrochemical bath that addresses endothermic and exothermic issues and keeps temperature constant during electrochemical reactions in large size samples. The electrochemical bath consists of an electrolytic bath, air compressor, glandless pump, water bath, and assembly heat change tubes. The electrochemical experiment tests included aluminium surface wet etching, electro-polishing on a 4-inch aluminium surface, electro-polishing on a 4 inch titanium surface, fabrication of 4-inch AAO template, fabrication of Ti-TiO2 interference membrane microstructure, fabrication of 6-inch TiO2 nanotube film, and electro-polishing of stainless steel. Acknowledgements This study was partially supported by a grant from the National Science Council, Taiwan (100-2918-I239-001-). References [1] J. Borowski, K. Bartkowiak, Physics Procedia 2010;5A: 449. [2] M. Chemingui, M. khitouni, G. Mesmacque, A.W. Kolsi, Physics Procedia 2009;2:1167. [3] A.J. Eifert, J.P. Thomas and R.G. Rateick, Scripta Materialia (1999);40:929. [4] G. E. Thompson and G. C. Wood: Trans. Inst. Metal Finishing (1980);58: 21. [5] H. Masuda and H. Yamada: Appl. Phys. Lett. 71 (1997) 2770. [6] K. T. Sunil and C. C.Hsueh: Chaos 12 (2002), 240. [7] H. Masuda and F. Hasegwa: J. Electrochem. Soc. (1997);144:127. [8] M. Paulose, H.E. Prakasam, O.K. Varghese, L. Peng, K.C. Popat, G.K. Mor, T.A. Desai, C.A. Grimes, J. Phys. Chem. C (2007);111:14992. [9] C.C. Chen, S. J, Hsieh, Journal of The Electrochemical Society, (2010);156:K125. [10] C.C. Chen, W .D. Jehng , L.L. Li, W.G. Diau, Journal of The Electrochemical Society, (2009);156:C304.
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Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
(a)
(c)
(b)
(d)
tophead O-ring plat e bas
Figure 1. Structure of rotating electrochemical mold: (a) the mold includes conducting rod, sample base, and reaction area; (b) exploded view of the mold showing rotating cover, O-ring, metal plate, and sample base; (c) schematic diagram of mold inside electrolytic bath, (d) schematic diagram of mold inside electrochemical system.
Figure 2 Thin films with nanostructure fabricated using the electrochemical mold and electrolytic bath: (a) four-inch diameter transparent AAO film; (b) transparent AAO film on a six-inch silicon wafer, (c) transparent AAO film on four-inch diameter glass.
(a) dead plate counter
dead plate
(b)
(c)
electrolyte silicone film working silicone film dead plate
Figure 3. Structure of flat electrochemical mold: (a) the counter electrode is fixed between two insulated boards with opening in middle; (b) the working electrode is fixed between silicone gel sheets and electrolytic bath is fixed on top of the working electrode; (c) the mold with counter electrode fixed on the working electrode structure.
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Chien Chon Chen et al. / Physics Procedia 25 (2012) 44 – 49
(a) heat change air Heat change tube
electrolyt
pump cooling
(b)
air input
(c
electrolyte input 1 2 4 3 electrolyte output
Figure 4. Electrochemical system including: (a) chemical reaction bath, cooling bath, heat change bath; (b) heat change tube consisting of pipes, elbows, and silicone gel tube connectors; (c) chemical reaction bath consisting of electrolyte input/output ports, air input port, and vacuum ports.
Figure 5. Electrolytic bath and mold-assisted surface treatments: (a) aluminium surface wet etching; (b) electro-polished 4inch aluminium surface; (c) microstructure of electro-polished aluminium; (d) microstructure of AAO template; (e) microstructure of electro-polished titanium; (f) Ti-TiO2 interference membrane microstructure; (g) anodic film on 6-inch titanium foil; (h) TiO2 nanotube microstructure; (i) electro-polished stainless steel microstructure, (j) nano-nickel wires microstructure; (k) porous WO3 microstructure; (l) AAO-TiO2 nanotube composite microstructure.